Counterpoint: I've reviewed multi-thousand line PRs (with dozens of commits) ... those took me days of 8 hour review, with multiple issues found. (To be fair, when I first skimmed it, it looked great to me, but a deeper dive found lots of things that could be improved.) These kinds of large PRs was how the gentleman I worked with did pairing and it worked out pretty well (surprisingly, don't try this at home).

I suspect this is the exception that proves the rule, not really an alternative rule.